1. Field of the Invention
This invention relates to polymeric antioxidants. In particular, it relates to novel polymeric N-substituted maleimide antioxidants and their preparation.
2. Description of the Prior Art
N-substituted maleimide compounds have been known to be useful as antioxidants in many different compositions such as rubbers, resins and other materials subject to the deleterious effects of oxidative aging. A major class of materials requiring oxidative stabilization are foodstuffs where extremely stringent requirements have been established which must be met by antioxidant compounds to be used in food industries. One of the most important of these requirements is that the compound be non-toxic, in addition to providing adequate protection against oxidation.
Several phenolic compounds such as butylated hydroxytoluene (BHT) and butylated hydroxyanisole (BHA) have found wide use as antioxidants in foodstuffs. Recently major questions have been raised concerning the possible toxicity of these compounds, resulting in restriction of their use of in the United States and actual prohibition in some European countries.
The development of safe alternatives is difficult for several reasons. Any of the known antioxidant compounds are of a nature such that upon ingestion and absorption from the gastointestinal tract into the body, many complex metabolic products are formed and since most antioxidants are capable of forming toxic derivatives and exact metabolic products are now known for most antioxidants, there almost always exists a substantial possibility of the development of a toxic compound. Additionally, even if it were possible to establish the non-toxicity of an antioxidant, the results would at best be only short term. It has recently become obvious in the food additive industry that only very long term testing can completely establish the activity of the many complex metabolic interactions which may occur upon ingestion and absorption of these compounds into the body.
It is possible however to overcome these problems when the antioxidant which is employed has a molecular size which prevents its being absorbed through the walls of the gastointestinal tract. This invention relates to such an antioxidant and to its preparation. The polymeric N-substituted maleimide antioxidants of the present invention may very easily be varied in molecular size so as to achieve the desired non-absorption through the walls of the gastointestinal tract, thus eliminating any possibility of dangerous metabolic derivatives being formed upon absorption into the body. The antioxidants of the present invention also find use in non-food applications where their high molecular weight leads to low volatility and improved carry-through properties, as well as other advantages.